ID
Index Name
Unit Description
471
0
MOT_Lsig
mH Motor leakage inductance (ASM) / stator
inductance (PSM)
472
MOT_LsigDiff
q-axis stator inductance variation (relative to
MOT_Lsig)
472
0
Lsig_q@I0
%
Inductance @ CurrentI0
472
1
Lsig_q@I1
%
Inductance @ CurrentI1
472
2
Lsig_q@I2
%
Inductance @ CurrentI2
472
3
Lsig_q@I3
%
Inductance @ CurrentI3
472
4
CurrentI0
%
Current I0 relative to MOT_CNom
472
5
CurrentI1
%
Current I1 relative to MOT_CNom
472
6
CurrentI2
%
Current I2 relative to MOT_CNom
472
7
CurrentI3
%
Current I3 relative to MOT_CNom
Table 7.6: “Advanced torque control - Saturation characteristic” parameters
7.3.6.1.2 K-T characteristic
In the overload range the output-side torque is reduced due to rising losses
(iron/copper losses). This behaviour can be compensated by P 479[0] - MOT_
TorqueSat.
P No.
Index Parameter name
Unit Function
479
MOT_TorqueSat
Motor torque as a function of the current
0 to 4
Nm
Torque; interpolation points 0 to 4.
5 to 9
A
Current; interpolation points 5 to 9.
Table 7.7: “K-T characteristic” parameters
7.3.6.2 Current observer
In the current control circuit, the calculation of voltage setpoints and PWM runtime
appears as dead time. This is the main factor determining the possible performance
of current control. The current observer eliminates this dead time to the greatest
possible extent by predicting current by means of a scanning step. In addition, many
synchronous servomotors exhibit harmonic components in the current control circuit.
The current observer suppresses these harmonic components so that they cannot
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ID No.: CB40859-001 Date: 11/2020
MSD Servo Drive - Device Help
127
7 Control
be passed on to the current controller. The disadvantage of the current observer is a
possible deviation between actual current and observed current. This can lead to an
overcurrent shutdown if the maximum current of the device or motor is controlled
stepwise.
The current observer is activated by P 433[0] - CON_CCON_ObsMode = TIME.
Adjust the time constant P 434[0] - Tf in the range from 0.062 ms to 0.5 ms. The
higher the time constant, the greater the smoothing effect of the observer – however,
the greater the possible deviations between actual current and observed current. On
the other hand, effects that do not correspond to the model are suppressed for the
control.
Another peripheral condition is that the electrical data of the motor must be well
defined.
l
Synchronous motors: see Section "Synchronous motor identification (rotary
and linear)" on page 46.
l
Asynchronous motor: see Section "Asynchronous motor identification" on
page 46.
Motor inductance (if necessary in connection with the saturation characteristic)
should be parameterised slightly too high.
ID
Index Name
Unit Description
433
0
CON_CCON_ObsMode
Select current observer mode
434
CON_CCON_ObsPara
Current observer parameters
434
0
TF
ms
Observer time constant
434
1
Kp
1/s
Proportional feedback gain
434
2
Tn
ms
Integral feedback time constant
434
3
Decoup
%
Scale decoupling
434
4
StatFF
%
Scale static voltage feed-forward
434
5
DynFF
%
Scale dynamic voltage feed-forward
434
6
FilterFF
ms
Filter voltage feed-forward
Table 7.8: “Advanced torque control - Observer” parameters
